The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A diesel engine combusts an air/fuel mixture to produce drive torque for a vehicle. Air is drawn into cylinders through an intake manifold. A fuel system injects fuel directly into the cylinders. The byproducts of combustion are exhausted from the vehicle via an exhaust manifold.
A high-pressure (HP) turbocharger and a low-pressure (LP) turbocharger are powered by exhaust gases flowing through the exhaust manifold and provide an HP compressed air charge and an LP compressed air charge, respectively, to the intake manifold. A bypass valve assembly may allow exhaust gas to bypass the HP turbocharger, thereby reducing the HP compressed air charge and an expansion ratio across the HP turbocharger. The bypass valve assembly typically includes a butterfly valve and a magnetic solenoid actuator. The magnetic solenoid actuator typically includes a solenoid coil and a magnetic core. The bypass valve is opened and closed by selectively supplying current through the solenoid coil. Control systems such as an engine control system may control the solenoid current to regulate opening of the bypass valve.
Traditional engine control systems, however, do not control the solenoid current as accurately or quickly as desired. For example, an engine control system may determine the solenoid current based on a solenoid temperature. However, solenoid variations and/or system aging may affect accuracy of the system. An engine control system may include a fast-response proportional-integral-derivative (PID) control scheme (e.g., 5 milliseconds) to control the solenoid current. However, a slow-response filter (e.g., 100 milliseconds) may be required to smooth the signal of feedback to remove short-term oscillations due to aliasing.